DISTANCE ACUITIES & VISUAL FIELDS

By: Carmen Willings teachingvisuallyimpaired.com

As part of the Functional Vision Evaluation, it is necessary to assess the student's distance visual acuities (including their intermediate and distance responses) as well as their visual fields. The technique used will vary depending on the students cognitive abilities.

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Distance Visual Acuity

Assess the student's distance vision using a combination of informal and formal devices. Assessment should include classroom activities, such as reading the chalkboard, as well as activities that take place outside the classroom, such as reading a banner in a hallway, catching a ball in a PE class, or identifying the bus after school. A formal distance-screening procedure should be included in the functional vision assessment to act as a comparison with clinical measures provided in the report of the clinical low vision specialist. Functional tasks using distance vision should include familiar an unfamiliar ones under different lighting conditions.

In the classroom, the most common activities for the use of distance vision are reading the chalkboard, dry erase boards, overhead transparencies or smart board. Also note the student's preferred seating arrangement for these activities, including the approximate viewing distance from the material and lighting. Other activities include reading bulletin boards, recognizing pictures and posters, viewing slides and videotapes, locating classmates and one's desk, seeing the teacher's facial expressions, and retrieving dropped objects from the floor.

Outdoor playing fields and indoor gymnasiums are difficult environments for some students with low vision because of variations in lighting and the need to respond to moving objects and people at different distances, such as when playing ball.

The cafeteria requires the use of distance vision for proceeding through the line, identifying foods, and recognizing the faces of classmates against a busy and colorful background.

Hallways necessitate the use of distance vision for recognizing friends, since the inability to recognize others can be misinterpreted as unfriendliness; otherwise, students with low vision may need to greet an approaching student aloud to receive a response and identify the speaker's voice. Also note the students ability to locate exit signs, room signs, locker, restroom, and names on doors. Note if the student can locate cafeteria, office, media center/library, health room, and auditorium.

The auditorium requires the use of distance vision for viewing a performance or a speaker during assembly. In this setting, it is important to note how the student responds if he cannot see enough detail to enjoy a performance: Does the student ask a classmate to provide essential information, use a monocular, or select a seat close to the front but away from friends and classmates?

Community opportunities to observe use of distance vision include: finding hidden objects, spotting airplanes and oncoming traffic, blowing bubbles, reading street numbers and signs, reading signs in stores, and watching birds. Distance acuity is used for visual tasks such as visual orientation to the environment, physical movements, and activities such as driving, sports and gross motor tasks. It is also needed for viewing the chalk/Smart-board in classroom, fast food menus, scoreboard at ball games and simple activities like seeing the classroom clock.

Depending on the results of the Distance Visual Acuity, the following strategies, recommendations, and accommodations may be necessary to meet the students unique visual needs:

Teach systematic search of the environment.

Preferential seating in class as well as in assemblies and movies and all demonstration lessons.

If a dry erase board is used, use bold, high contrast markers on clean board.

May need verbal descriptions of demonstrations and films/movies.

Visual Fields

The central visual field is the "what" system, while the peripheral visual field is the "where" system. The visual field is the entire area of vision that can be used without shifting the eyes or moving the head, encompassing 180 degree arcs. Assess the student's visual fields including the student's preferences or limitations. Observe the students response to materials presented in the central visual field and to the peripheral visual fields. Note where the student responds to materials. Estimate the number of degrees from the nose.

Note other signs of possible field loss including: over-scanning; eccentric viewing; holding object to the side, up, or down to inspect it; stumbling over low-lying objects; functional peripheral vision is often a source of distractibility. A student's scanning of an array of objects or looking for a missing object can demonstrate his functional visual field at near point. For example, a compensatory head turn suggests a peripheral field loss to the side of the head turn, since the student has learned to compensate by moving the usable visual field toward the side where information is missing.

The performance of activities, such as scanning a map or doing a word-search puzzle, can also suggest where scotomas (areas of absent vision) may be located, because if students are asked to keep their heads perfectly still while doing them, they may miss information in some areas of the tasks. Students who walk with their heads turned slightly to one side may be compensating for a difference in visual fields. Eye preference, evidenced in typical tasks, can also be evaluated.

Observe special visual behaviors and repetitive behaviors including eccentric viewing, stereotypical behaviors, and fluctuating visual abilities. Observe whether the student uses corrective lenses and tolerates them. Also indicate if the student has received Orientation and Mobility services. Note how the student currently travels indoors, outdoors, in familiar and in unfamiliar environments.

The absence of a full (180 degrees) peripheral field may cause difficulty in sports and social difficulty due to not seeing those in their visual field or by using an odd posture in order to see. They also may not see downward flight of stairs or a curb. It also may limit the amount of letters/words can see at a time.

Depending on the results of the Visual Fields Testing, the following
strategies, recommendations, and accommodations may be necessary to meet
the students unique visual needs:

Seat to left/center/right side of room depending on field of vision

Caution in PE or at recess with fast moving balls or objects

Train the student to scan the environment prior to entering a new area